Cooling apparatus with conveyor

ABSTRACT

A method of and apparatus for cooling a body which is a bad conductor of heat, the method consisting of displacing the body from the inlet to the outlet of an elongated cooling zone in a current of a cooling fluid in the gaseous state circulating wholly in said zone in the same direction as that of the displacement of the said body, a difference in temperature being maintained at the inlet of the said zone, between said body and said current at least equal to 150*C. The cooling fluid may be nitrogen and the body to be cooled may be made of an elastomer or polymer material. The apparatus comprises a thermally insulated tunnel, an evaporator for the cooling fluid in the liquid form, comprising a conduit in heat exchange relation with the interior of the tunnel and orifices for the introduction of the fluid in the gaseous state at the inlet of the tunnel.

Write States Patent [191 Caillat et al.

[ July 17, 1973 COOLING APPARATUS WITH CONVEYOR [22] Filed: May 20, 1971- [21] Appl. No.: 145,338

[30] Foreign Application Priority Data May 22, 1970 France 7018787 [52] US. Cl. 62/380 [51] Int. Cl. F2511 25/04 [58] Field of Search 62/62, 63, 64, 373, 62/374, 375, 376, 380; 99/197, 198

[56] References Cited UNITED STATES PATENTS 3,403,527 10/1968 Berreth et a1 62/380 X 13,427,820 2/1969 Hart 62/380 X 3,431,745 3/1969 Harper et al.... 62/380 X 3,455,120 7/1969 Schlemmer..... 62/380 X 3,228,206 1/1966 Lockerby.... 62/375 X 3,345,828 10/1967 Klee et a1 62/63 3,115,756 12/1963 Overbye 62/380 X 3,287,932 11/1966 Schlemmer, Jr... 62/374 3,315,480 4/1967 Rich 62/63 3,398,788 8/1968 Brunson 62/380 X 3,605,428 9/1971 Smith et al 62/64 Primary Examiner- Meyer Perlin Assistant Examiner-Ronald C. Capossela Attorney-Young & Thompson 57 ABSTRACT A method of and apparatus for cooling a body which is a bad conductor of heat, the method consisting of displacing the body from the inlet to the outlet of an elongated cooling zone in a current of a cooling fluid in the gaseous state circulating wholly in said zone in the same direction as that of the displacement of the said body, a difference in temperature being maintained at the inlet of the said zone, between said body and said current at least equal to 150C. The cooling fluid may be nitrogen and the body to be cooled may be made of an elastomer or polymer material. The apparatus comprises a thermally insulated tunnel, an evaporator for the cooling fluid in the liquid form, comprising a conduit in heat exchange relation with the interior of the tunnel and orifices for the introduction of the fluid in the gaseous state at the inlet of the tunnel.

4 Claims, 6 Drawing Figures 1 COOLING APPARATUS WITH CONVEYOR The present invention relates to a method of cooling of a substance which is a bad conductor-of heat. It relates in particular to a method permitting the cooling of a theme-deformable material such as a plastic material, or of an elastomer such as rubber.

The invention also relates to a cooling device enabling the said method to be carried into effect.

By a substance which is a bad conductor of heat there is meant any non-metallic object or material having a low heat conductivity and also a low thermal diffusiveness. There will comply for example with this definition a rubber, a plastic material, a resin, a glue, but also food products, pasty chemical products, etc.

Certain industrial manufactures necessitate cooling of a material which is a bad conductor of heat. Thus, when objects are manufactured by hot-forming a thermo-deformable material such as a polymer, it is essential to cool the objects formed effectively when the latter are liable to be deformed in a non-reversible manner during the course of operation which follows the heat-forming, or during the course of storage, in consequence when the latter are liable not to comply with the characteristics and specifications of the finished objects. For example, in the case of vehicle joints manufactured by hot extrusion of a mass of rubber, it is inevitable that certain zones of the said joints are deformed by compression or that certain coils are stuck together when these objects are not correctly cooled immediately after shaping.

in order to cool objects or materials which are bad conductors of heat, these latter are generally moved in a current of a cooling fluid, such as water or air. The major drawback of these usual methods resides in the slow rate of cooling obtained, since the material to be cooled offers very high resistance to the heat flux.

Cooling thus becomes a very long operation which substantially reduces the productivity of a line of manufacture. It further necessitates the use of installations of large bulk, since the tunnels generally employed must have sufficient length to obtain a high contact time between the cooling fluid and the object to be cooled.

The present invention proposes to provide a remedy for all these disadvantages.

The invention has therefore for its object a method and a device enabling the high thermal resistance of a bad conductor of heat to be compensated and thus permitting the said body to be cooled very rapidly.

The invention is concerned with a method of cooling of 'a body which is a bad conductor of heat, according to which the said body is displaced from the inlet to the outlet of an elongated cooling zone in a current of cooling fluid which closely envelops the said body and circulates as a whole with the body substantially from the inlet to the outlet of the said zone, and in which there is maintained a temperature difference at least equal to 150C. between the saidfbody and the said current at the inlet of the said zone.

The invention thus permits essentially a compensation of the high resistance opposed by the body to be cooled to the heat fluxes, by a large difference of temperature between the cooling flow and the body to be cooled. This temperature difference is maintained for a large part of the displacement of the said body in the cooling zone, since the said flow and the said body to be cooled circulate in a coextensive direction and more lower to this said zone but higher than the zone of the temperatures at which the material becomes brittle, there is maintained at the inlet of the said zone a difference in temperature between the said body and the said current having a value at least equal to 350C.

Any cooling according to the invention can thus be effected with a time of contact between the cooling fluid and the object to be cooled which is substantially less than that necessary in a method in which the body to be cooled and the cooling current circulate in counter-flow with respect to each other. It follows that the size of the corresponding cooling installations is substantially reduced.

The cooling fluid is preferably introduced substantially at the inlet of the said zone, essentially in the gaseous form, at a temperature in the vicinity of its boiling temperature. There is thus avoided the oelefaction phenomenon which would be encountered in the case of a simple spraying of a cryogenic liquid at the inlet of the cooling zone on the body to be cooled. The thermal exchanges between the cooling fluid and the body to be cooled are therefore further accelerated. In the case where the cooling fluid is a cryogenic liquid such'as liquid nitrogen, any loss of the said liquid is furthermore prevented, while operating, according to the fluid employed, at the lowest possible temperature. In the case where the cooling fluid is nitrogen, this makesit possible to operate in the gaseous phase from the inlet of the cooling zone, at a temperature in the vicinity of l96C.

Advantageously, when the cooling fluid is introduced at the inlet of the cooling zone in an essentially gaseous form at a temperature in the vicinity of its boiling point, the said fluid is vaporized in the liquid form before its introduction into the said zone, by exchange of heat in the said zone between the said body and the said liquid, in particular by exchange of heat between the said current and the said liquid.

This enables a good frigorific efficiency to be obtained and therefore a smaller quantity of the cooling fluid is consumed, since there are utilized not only the frigories of the vaporized form of the cooling fluid but also the frigories of vaporization of the liquid form of the said fluid.

The invention also relates to a cooling device permitting the method according to the invention to be carried into effect. A cooling device according to the invention comprises a heat insulating wall forming a tunnel, means for diaplacing said body fromthe inlet to the outlet of the said tunnel, circulation means in the interior and over the whole length of the said tunnel of a current of a cooling fluid essentially in the gaseous form, the said circulation means comprising means for introducing the said fluid arranged substantially at the inlet of the said tunnel, an evaporator for the said fluid in the liquid form, arranged wholly in the interior of the said tunnel and comprising a conduit for the said fluid in heat-exchange relation towards the interior of the said tunnel, one extremity of which communicates with the said introduction means.

There is described below one form of embodiment of the invention, given without limitation, reference being made to the accompanying drawings, in which:

FIG. 1 shows a side view, partly in section taken along a longitudinal plane of symmetry, of a cooling device according to the invention. The scale used for the heights is greater than that employed for the lengths in order substantially to clarify the drawings;

FIG.2 shows a view in cross-section of the device taken along the line A-A of FIGJ, to a larger scale;

FIG.3 shows a view in cross-section of the device taken along the line 3-8 of FIG.1, to a scale identical with that of FIG.2;

FIG.4 shows a view in cross-section of the device taken along the line C-C of FIG], to a scale identical with that of FIG.2;

FIG.5 shows a plan view, partly in cross-section, to a larger scale, of the portion 24 of FIG.1;

FIG.6 is a graph relating to the conditions of operation of the device shown in FIGJ. For given working parameters, it gives the consumption of the device in liquid nitrogen, expressed in litres per hour as a function of the speed of passage in the interior of the device of the objects to be cooled, expressed in metres per hour.

According to FIGS.1 to 5, the device of substantially elongated form comprises a heat-insulation wall forming a tunnel having a symmetrical aspect with reference to a longitudinal plane. This wall comprises three sections, 1, 2, 3 in succession from left to right, the sections 1 and 3 being of equal length.

Each of the sections 1, 2, 3 comprises a casing 4 closed by a cover 5. Each casing 4 has a transverse section of U-form and is constituted by a heat-insulation material 6. This material is covered externally by a metal sheet 7 having a U-profile and internally by a metal sheet 8 having the same profile, the two sheets 7 and 8 being superimposed on the edge of the material along the upper edge of each lateral wall 9 of each casing 4.

Each cover has a square transverse section and is constituted by the same heat-insulation material 6. This material is covered over three sides of the square section by a metal sheet 10, two excrescences of which form flanges I1 and 12. An upper flat metal sheet 13 covers the said cover over the fourth side of the square section, the sheet 13 being supported on the flanges 11 and 12. Each cover 5 is housed in the upper inside portion of each casing 4 between the lateral walls 9, each cover 5 being supported against the upper edge of the walls 9 by means of the flanges 11 and 12.

The various sections 1, 2, 3 are joined together. For this purpose, joints I4 and 15 are respectively arranged between thecasings 4 of the sections I and 2 and the casings 4 of the sections 2 and 3. Similarly, joints l6 and 17 are arranged respectively between the covers 5 of the sections I and 2 and the covers 5 of the sections 2 and 3.

At each extremity of the tunnel, on the sections 1 and 3 are respectively fixed on each casing 4 and each cover 5, a metal junction sheet 18 and a junction sheet 19. Plugs 20 made of the'material 6, of rectangular transverse section and small thickness with respect to the length of the tunnel, close at each extremity of the tunnel, the lower internal portion of each casing 4 so as to form between the cover 5 and the plug 20 a space forming respectively in the section 1 and the section 3, an inlet window 21 and an outlet window 22. Each plug is fixed by means of a metal sheet 23 which covers it, to the junction sheet 18. The body or object to be cooled moves inside the tunnel constituted as has just been described, from the inlet window 21 to the outlet window 22.

The cooling device further comprises an evaporator 24 for a cooling fluid in the liquid form, arranged wholly inside the said tunnel. This latter is entirely supported by a horizontal plate 25 fixed by means of two ribs 26 on the portion of the metal sheet 8 of the section 1 forming the internal lateral envelope of the casing 4.

The evaporator 24 is constituted essentially by a conduit or tube 27 of great length, inside which the cooling fluid circulates between an upstream extremity 28 and a downstream extremity 29. The tube 27 comprises two parts of equal length 27a, and 27b extending, as shown in H681 and 5 along the direction of the tunnel alternately and successively from an intermediate position between the inlet 21 and the outlet 22 to a position substantially adjacent to the said inlet. The upstream extremity 28 and downstream extremity 29 are furthermore adjacent to each other. The cooling fluid thus passes through the part 27a and the part 27b respectively in an opposite direction and in the same direction as that of the movement of the object to be cooled.

In addition, the tube 27 is made in the form of a coil of straight rectangular section, the parts 27a and 27b of which are of opposite pitch and are displaced one with respect to the other. Such a configuration of the tube 27 may be obtained by bending it back like a hairpin and winding this latter round a parallelepiped mandrel.

The tube 27 having the form which has just been described, is incorporated in an envelope in the form of a box with a straight annular and rectangular section,

comprising an internal parallelepiped metal wall 31, around which the tube 27 is wound and with which the parts 27a and 27b are in thermal contact. These latter are therefore in thennal exchange with each other through the intermediary of the heat exchange wall 31 towards the interior of the tunnel, and the conduit 27 is in consequence in heat-exchange relation towards the interior of the said tunnel.

The said envelope also comprises a parallelepiped external metal wall 32 in contact with the tube 27 along the outer contour of the coil. The envelope comprises at its two extremities, on the side of the inlet window 21 and the outlet window 22 respectively, two annular plates 33 joined to the internal wall 31 and the external wall 32 by a brazing bead.

The downstream extremity 29 of the tube 27 opens freely into the interior 30 of the said envelope in the vicinity of the upstream extremity 28. The internal wall 30 is provided with a plurality of holes or orifices 37 or other means enabling the cooling fluid to be introduced into the vicinity of the entrance of the tunnel (see FIG. 1 and 5), since the downstrem extremity 29 communicates with the orifices 37 through the intermediary of the interior 30 of the said envelope.

The external wall 32 is traversed in a fluid-tight manner at its extremity on the side of the outlet window 22 by a female end-piece 34 rigidly fixed to the upstream extremity 28 of the tube 27. This female end-piece is connected on the male end-piece 35 of a tube 36 passing through the lateral wall 9 of the casing 4 of the sec tion 1; the tube 36 ensures the supply of cooling fluid to the tube 27 from an external source (not shown).

The body or object to be cooled is moved inside the tunnel from the inlet window 21 to the outlet window 22 by means of a conveyor belt 38 orother means of displacement. The conveyor belt 38 is closed on itself in the form of an'elongated loop around two pulleys 39 and 40 located in the interior of the tunnel in the vicinity of the inlet window 21 and the outlet window 22 respectively of the cooling device. The carrier side of the conveyor belt 38 passes inside the coil 27 which constitutes an annular assembly surrounding at a distance at least a part of the conveyor belt 38. The belt 38 is made of a fabric of stainless steel wires.

Each of the pulleys 39 and 40 is fixed on a shaft 41 by means of a headless screw 42. The shaft 41 passes right through the pulley 39 or 40, together with the lateral walls 9 of the cooling tunnel. Each of the pulleys 39 and 40 is provided with'a groove 43, inside which is placed a rolling band 44 of polytetrafluoroethylene with which the conveyor belt is in contact. Two reinforcement plates 45 are arranged against the metal sheet 8 on each side of the pulley 39 or 40 in order to reinforce the part of the tunnel in the vicinity of the rotation shaft 41.

When the belt 38 carries an object to be cooled, it is supported: from the inlet window 21 to the outlet window 22 a first supporting plate 46 and then by the intemal' metal wall 31 of the evaporator 24, and then by a second supporting plate 47. The supporting plates 46 and 47 are fixed, like the supporting plate 25 of the evaporator 24, on the metal sheet 8 of the casing 4. The side of the belt which does not carry any object to be cooled is supported at its mid-point by a tension roller 48 located inside the section 2 of the cooling device.

The tension roller 48, shown in the lower position in FIG. 4, is provided with a groove 49 occupied along a fraction of its circumference by the conveyor belt 38. The roller 48 is capable of rotating about a shaft 50 supported by two arms 51 and 52 which are in turn fixed to a tube 53 about which are fixed the arms 51 and 52. The tube 53 is rigidly fixed to a shaft 54 passing into the interior of the tube 53 by means of a screw 55. The shaft 54 is held in position at one extremity in a hole 56 pierced through the metal sheet 8 and passing over a short length into the material 6.

At the other extremity, the shaft 54 passes right through the lateral wall 9 of the tunnel and isprovided outside the tunnel with a lever 57 adjustable in position, for example by means of a spring (not shown). Two reinforcing plates 60 are provided to support the shaft 54.

The coolingdevice further comprises means for circulatingin the interior and over the whole length of the said tunnel, the current of cooling fluid in the gaseous form. In addition to the introduction orifices 37, these means comprise a number of shutters 58, 59, 61 of polytetrafluoroethylene, placed in the interior of the tunnel, respectively in the vicinity of the inlet window 21, in the section 2 and in the section 3. Each of these shutters extends between the lateral walls 9 and the conveyor belt 38 up to' the cover 5. Each is capable of pivoting about a shaft 62. These shutters compel the flow of cooling fluid to circulate exclusively from the inlet to the outlet of the tunnel. In particular, the shutter 58 placed between the inlet window 21 and the evaporator 24 prevents the outlet of the gaseous flow through the inlet window21.

There will be described below the operation of the cooling device according to FlGS.1 to 5.

The belt 38 is given a movement of translation by starting up the rotation of one of the pulleys 39 or 40 or of both, by means of an appropriate driving source. Objects or bodies which are bad conductors of heat, having a given inlet temperature, pass into the interior of the tunnel through the inlet window 21. They are then moved or conveyed in the interior of the tunnel in the direction of the arrows shown in FIG.1, by the belt 38, and pass out of the tunnel at an outlet temperature lower than the inlet temperature, through the outlet window 22.

The smallest straight section of the tunnel, defined according to FlG.3 by the internal contour of the coil 27 and limited towards the bottom by the conveyor belt 38, corresponds substantially to the transverse dimensions of the objects 80 to be cooled.

In operation, the tube 27 is supplied, for example with liquid nitrogen, by a transfer line connected at one extremity to the tube 36 and at the other extremity to a receptacle of liquid nitrogen (not shown). The nitrogen passes in liquid form into the tube 27 at its upstream extremity 28, at a temperature substantially equal to its boiling point, i.e in the vicinity of -1 96C. The liquid nitrogen is almost completely vaporized during its passage through the interior of the tube 27. The heat necessary for this vaporization is obtained by an exchange between the objects to be cooled circulating in the interior of the tunnel and the nitrogen passing through the tube 27.

The major part is obtained by exchange through the internal metal wall 31 with a current of cooling fluid essentially in the gaseous form, circulating inside the manel and becoming heated by contact with the objects to be cooled. Another part is obtained by radiation from the said objects to the metal wall 31. The nitrogen passes out at the downstream extremity 29 of the tube 27, for the major part in the gaseous state at a tempera ture in the vicinity of 77K. The gaseous nitrogen obtained at 29 then passes through the interior 30 of the envelope of the evaporator 24 in the opposite direction to the movement of the objects to be cooled. It is then introduced and projected into the inlet of the tunnel through the holes 37 on to the objects to be cooled, and therefore in the gaseous state at a temperature in the vicinity of l96C. and at a pressure higher than the pressure outside the tunnel.

It then constitutes the said current of cooling fluid. This latter circulates wholly, at high speed, by forced convection, from the inlet to the outlet of the tunnel. It thus circulates with the said objects'which it closely surrounds in view of the relative dimensions of the section of the tunnel previously defined and that of the said objects. The circulation in concurrent flow of the objects to be cooled and the cooling currents is obtained by means of the various shutters 58, 59, 61, and of the inlet over-pressure.

The cooling gaseous flow thus becomes heated in contact with the objects which it cools, and is then evacuated through the outlet window 22 after having given up, through the wall 31, to the liquid nitrogen cir culating in the tube 27, a part of the heat taken up by contact with the objects to be cooled.

By way of example, the graph of FIG.6 gives the consumption of liquid nitrogen of a device according to the invention, as a function of the speed of movement of the objects to be cooled, when these objects pass into the tunnel at 180C. and pass out at +SC., when the constituant material has a density of 1.32, a specific calorific capacity evaluated at about I calorie per gram per degree C. and a thermal conductivity of 2.3 X 10 What we claim is:

l. A cooling device comprising a heat-insulating wall forming a tunnel, means for moving bodies to be cooled through said tunnel, means for conveying a refrigerating liquid in indirect heat exchange in the interior to the tunnel thereby to evaporate the liquid to a vapor, and means for introducing said vapor into the tunnel, said liquid conveying means comprising a conduit of great length constituted by different sections in heat exchange with each other, said conduit being a coil in the form of an annular assembly surrounding at least a part of said moving means.

2. A cooling device as claimed in claim 1, in which said coil comprises two portions of opposite pitch displaced lengthwise of the tunnel with respect to each other.

3. A cooling device comprising a heat-insulating wall forming a tunnel, means for moving bodies to be cooled through said tunnel, means for conveying a refrigerating liquid in indirect heat exchange in the interior of the tunnel thereby to evaporate the liquid to a vapor, and means for introducing said vapor into the tunnel, said liquid conveying means comprising a conduit of great length constituted by different sections in heat exchange with each other, said different sections being in thermal contact with a heat exchange wall inside said tunnel and extending lengthwise of said tunnel, said wall forming part of an envelope in the form of a box enclosing said conduit, said vapor-introducing means opening into the interior of said envelope which in turn communicates with the interior of the tunnel.

4. A cooling device as claimed in claim 3, in which said envelope comprises at least one orifice for the introduction of said vapor into the inlet of the tunnel.

* t t i I 

1. A cooling device comprising a heat-insulating wall forming a tunnel, means for moving bodies to be cooled through said tunnel, means for conveying a refrigerating liquid in indirect heat exchange in the interior to the tunnel thereby to evaporate the liquid to a vapor, and means for introducing said vapor into the tunnel, said liquid conveying means comprising a conduit of great length constituted by different sections in heat exchange with each other, said conduit being a coil in the form of an annular assembly surrounding at least a part of said moving means.
 2. A coolIng device as claimed in claim 1, in which said coil comprises two portions of opposite pitch displaced lengthwise of the tunnel with respect to each other.
 3. A cooling device comprising a heat-insulating wall forming a tunnel, means for moving bodies to be cooled through said tunnel, means for conveying a refrigerating liquid in indirect heat exchange in the interior of the tunnel thereby to evaporate the liquid to a vapor, and means for introducing said vapor into the tunnel, said liquid conveying means comprising a conduit of great length constituted by different sections in heat exchange with each other, said different sections being in thermal contact with a heat exchange wall inside said tunnel and extending lengthwise of said tunnel, said wall forming part of an envelope in the form of a box enclosing said conduit, said vapor-introducing means opening into the interior of said envelope which in turn communicates with the interior of the tunnel.
 4. A cooling device as claimed in claim 3, in which said envelope comprises at least one orifice for the introduction of said vapor into the inlet of the tunnel. 